Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 asm updates from Ingo Molnar:
 "A single commit micro-optimizing short user copies on certain Intel
  CPUs"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/uaccess: Optimize copy_user_enhanced_fast_string() for short strings

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index c5959576c315..020f75cc8cf6 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -37,7 +37,7 @@ ENTRY(copy_user_generic_unrolled)
         movl %edx,%ecx
         andl $63,%edx
         shrl $6,%ecx
-        jz 17f
+        jz .L_copy_short_string
 1:      movq (%rsi),%r8
 2:      movq 1*8(%rsi),%r9
 3:      movq 2*8(%rsi),%r10
@@ -58,7 +58,8 @@ ENTRY(copy_user_generic_unrolled)
         leaq 64(%rdi),%rdi
         decl %ecx
         jnz 1b
-17:     movl %edx,%ecx
+.L_copy_short_string:
+        movl %edx,%ecx
         andl $7,%edx
         shrl $3,%ecx
         jz 20f
@@ -174,6 +175,8 @@ EXPORT_SYMBOL(copy_user_generic_string)
  */
 ENTRY(copy_user_enhanced_fast_string)
         ASM_STAC
+        cmpl $64,%edx
+        jb .L_copy_short_string /* less then 64 bytes, avoid the costly 'rep' */
         movl %edx,%ecx
 1:      rep
         movsb